This slide circular tray will not work in a Keystone projector and on the discription it says it fits many projector, in fact some of the projectors it say it will fit i have trays for those makes and they work in my Keystone if I use the adaptor ring for them. The one they are selling here will not accept the adaptor ring. Anyway, I think they should say what projectors they won't work on so people won't have to go thru what I went thru[...]